Turkish riot police take up position at Taksim Square in Istanbul. Police have been accused of using excessive force against protesters in Gezi Park and all over the country. Photograph: Osman Orsal/Reuters

Tired after spending the second night in a row sleeping on his shield on a city centre pavement, deprived of washing and toilet facilities, hungry and thirsty, the Turkish police officer sounded rather fed up.

"We have now been working for 56 hours straight," he said.

The 30 exhausted riot police officers sitting on a pavement in a side street by Istanbul's Taksim Square had had one hour of rest the night before. Some of them dozed, their heads against a wall.

The officer lifted his security vest, filled with teargas cartridges. "Between this, the teargas gun and my shield, I carry about 10kg. But after a couple of hours on duty, it feels like I am carrying 100."

His colleague interrupted: "All of us are completely exhausted. We have been working like this ever since the protests began two weeks ago." Another laughed. "We are too tired to even do this interview." They requested anonymity for fear of repercussions.

After almost a fortnight on the frontline of the most significant street unrest seen in Turkey in years, the officers are disgruntled at the way they are being treated by their superiors. They all criticised the lack of facilities for riot police on duty around Taksim Square.

"There are no toilets, no washrooms," said one. "We have to ask in hotels and shops. That's unacceptable." Others join in: "Our food supply is very bad. Sometimes there is nothing to eat all day, sometimes the food has gone bad."

Some say that they buy their own food instead, but expenses cannot be claimed.

"How are we supposed to respect other people's rights if nobody respects ours?" one police officer wondered.

The police have been accused of using excessive force against the protesters in Gezi Park and in demonstrations that spread all over the country. According to the Turkish Medical Association, 4,345 people sustained injuries as a result of the police's heavy-handed interventions. Three are still said to be in critical condition.

Faruk Sezer, head of the newly formed police union Emniyet-Sen, linked the police violence directly to a lack of sleep and mistreatment of police officers by their superiors.

"How are people supposed to respect the police when they see them sleeping on the pavement in their uniforms? This is not how the governor and the Turkish police directorate should treat their employees. It's inhuman," he said.

"Fatigue and constant pressure lead to inattentiveness, aggression and a lack of empathy. It's irresponsible to keep riot police on duty for such long hours without any rest."

He added that around 500 riot police have been injured over the past two weeks. In Adana, one policeman fell off a bridge and died, an accident reportedly caused by exhaustion.

Police officers in Turkey have major problems attempting to organise to represent themselves and press for better working conditions. So far attempts to form a democratic union have been met by bans and threats of disciplinary action. The police officers who founded Emniyet-Sen seven months ago have all been suspended.

Despite a court decision to the contrary, neither the Turkish government nor the police directorate recognise the union, and new recruits to the organisation – so far, Emniyet-Sen counts about 10,000 members – face disciplinary threats and investigation.

"Police officers like everyone else have the right to join a union, a fundamental right stemming from the right to organise and the right to freedom of association," said Andrew Gardner, Turkey researcher for Amnesty International.

"Given the events of the last few weeks it is particularly important that police officers are given access to such representation, with direction being given from their superiors to use excessive force against demonstrators."

In Gezi Park, where the protesters have been camping for a fortnight, many taking part underline that their quarrel is not with the police.

"We do not fight or want to fight against the police," said Hamit Menemencioglu, 21. "Our criticism is against the Turkish government, and they should be the ones dealing with us, talking to us."

Just a few streets away, the officers could not agree more.

"These protests will not be quashed with teargas," said one. "There needs to be dialogue. They need to find a consensus." His colleagues nod. "We do not enjoy fighting citizens, and we hope that there will be an end to this soon."